Many industrial operations utilize apparatus which generates a considerable amount of heat; and this heat is often removed by circulating a coolant into heat exchange relationship with the heat source. In some operations, after the coolant is heated by the heat source it is cooled and recirculated. The extracted heat may or may not be utilized.
In many systems which utilize water as the coolant, the water is required to have a low level of dissolved gases and dissolved and suspended solid particles. Dissolved gases are typically removed by deaerating the water. Solids may be removed by suitable filters and other devices of a type which depends upon the nature and size of the impurities and the extent to which they must be removed. Even if acceptably clean water is initially introduced into the system, it may pick up or accumulate contaminants from within the system, and these contaminants often have to be removed on either an intermittent or continuing basis.
Boilers or other apparatus that include a reservoir which remains at least partially filled with hot water may also accumulate unaceptably large amounts of impurities with time. Intermittent blowdown of these reservoirs to remove the accumulated impurities is well known in the art. For example, in U.S. Pat. No. 3,215,126 steam is used to drive a turbine. The turbine exhaust is condensed and the water therefrom is deaerated. The deaerated water is passed through a heat source whereupon at least a portion of it is converted to steam. The heated water and steam is then sent to a stream drum which includes a reservoir of liquid water maintained at saturated temperature. The steam is used to drive the turbine and the liquid in the steam drum is blown down intermittently to remove impurities which build up therein. The blowdown is shown being fed to the deaerator. Other U.S. patents which show the use of filters, deaerators, and blowdown to remove contaminants include the following: U.S. Pat. Nos. 1,543,727; 1,895,635; 1,904,900; 2,001,249; 2,018,803; 2,193,795; 2,258,167; 3,200,568; and 3,668,838.
In commonly owned U.S. Pat. No. 3,982,962, FIG. 1 shows a fuel cell power plant wherein water is continuously circulated and recirculated through the fuel cells as a coolant therefor. Heat from the cells converts a portion of the coolant to steam, and that steam is used in a steam reform reactor to produce hydrogen fuel for the fuel cells. Make-up water for the coolant loop is obtained by condensing water from the fuel cell reactant gas streams. The coolant water picks up impurities as it recirculates through the system and also from the impurities in the make-up water added thereto. It is desirable to have an automated system for delivering make-up water, for removing impurities from the make-up water before adding it to the recirculating coolant, and for removing impurities as they build up in the recirculating coolant loop. Commonly owned U.S. Pat. No. 4,120,787 describes a system for deaerating and purifying the condensate from fuel cell reactant gas exhaust streams; however, an efficient, economical, automated method for both cleaning the condensate as well as maintaining the purity of a continuously recirculating coolant is presently not described in the art. Of general interest relating to the state of the art in automated or self-controlled water cleaning systems is U.S. Pat. No. 3,454,491 which is a closed loop automated system for filtering and deionizing water. Steam flow into the system is controlled by a valve operated by a temperature sensor positioned downstream in the system to shut off the steam flow if temperatures downstream exceed the temperature limitations of an ion-exchange column.